1. Field of the Invention
This invention relates to medical catheters, particularly those for opening lesions in arteries.
Catheters designed for steering through a tortuous path of small arteries, such as the coronary arteries, have been of two general types. One type slides over a separate guidewire. The second type involves a guidewire built into the catheter. The guidewire and catheter are inserted in the artery as a unit.
Such catheters built on a wire are steered through the arteries by directing a bent tip in the proper direction to enter a branch. The guidewire is rotated to turn the bent tip in the proper direction. A known problem in the prior art on-the-wire catheters is that rotation of the guidewire may cause the balloon in the catheter to twist and wrap up around the guidewire. This will cause later problems in inflation and deflation of the balloon.
This problem is taught in U.S. Pat. No. 4,664,113 which explains the problems with balloon wrap. That patent discloses a typical prior art device where the distal end of the balloon is fixed directly to the guidewire. When the guidewire rotates, the balloon twists. In an attempt to mitigate this problem, that patent limited rotation of the wire. Such limitations on rotation are well known in other catheter arts, but is found to be necessary for a particular functional purpose in wires of the type disclosed with a balloon bonded directly to a guidewire. What is needed in the art is a balloon structure which performs the functions of traditional on-the-wire catheters, but is not subject to the balloon wrap problem of the style in U.S. Pat. No. 4,664,113.
One other attempt to solve this problem is a design such as the PROBE catheter from USCI. This has a guidewire independent of the end of the balloon. However, the device does not have sufficient structural integrity for retaining the guidewire relative to the catheter structure. A structure is needed which prevents wrap but which is structurally sound and preserves the integrity of the tip area.